Downstream areas of the Blue River and Little Blue River basins are highly affected by urban development, according to a new U.S. Geological Survey study that compares the aquatic-life status of streams in the Kansas City, Mo. metropolitan area using macroinvertebrate populations as an indicator of stream health.

This study increases our understanding of aquatic life and water quality in urban streams. The differences in aquatic-life status of the Blue River and Little Blue River indicate how stormwater, wastewater discharges, and upstream reservoirs affect urban streams.

Macroinvertebrates, or animals without a backbone that are visible to the unaided eye, were collected in the Blue River basin in Kansas City, Mo., and the Little Blue River and Rock Creek basins in Independence, Mo., as part of two urban water-quality studies to assess the aquatic-life status of urban streams. Aquatic macroinvertebrates, which include insects, worms, mussels, and crayfish, are at the base of the food chain in aquatic environments. They are the main food source for many other animals such as fish and ducks, so scientists commonly use them to study the ability of a stream to support aquatic life.

"None of the samples collected from the Blue River had characteristics considered to be fully able to support aquatic life," said USGS co-author Heather Krempa. "However, about one out of ten spring samples and about four out of ten fall samples from the Little Blue River did have characteristics considered to be fully supporting of aquatic life."

Macroinvertebrate samples were collected from streams and analyzed several ways, including counting the total number and types of macroinvertebrates collected, grouping them based on feeding methods, and calculating the tolerance of the macroinvertebrates to pollution and environmental stress. Samples were scored to provide information about the stream at the sample location and were compared among sites. The aquatic-life status scores for the Little Blue River and its tributaries were higher, indicating more optimal conditions, than for the Blue River and its tributar­ies.

A Stream Condition Index that combines several different measures of macroinvertebrate populations was used to describe and assign three categories to the stream sites: non-, partially, and fully biologically supporting.

Wastewater-treatment plant discharges during low flows and combined sewer overflows into the Blue River lower aquatic-life scores and likely reduce water quality. Separate stormwater sewer system and reservoir releases to the Little Blue River may raise water quality and aquatic-life scores.

The study, "Assessment of Macroinvertebrate Communities in Adjacent Urban Stream Basins, Kansas City, Missouri, Metropolitan Area, 2007 through 2011," has been released as USGS Scientific Investigations Report 2012-5284 and is available online.